1. Field of the Invention
This invention pertains to the coating of sugarless tablets. More particularly, this invention pertains to the coating of moisture sensitive core material with a primary coating layer to protect the core material from the moisture employed in subsequent coating steps. Specifically, the invention is directed at an edible coated composition which comprises (a) a core material comprising sorbitol, (b) a primary coating layer comprising zein over the core material, and (c) a sugarless secondary coating layer over the primary coating layer. The present invention also pertains to methods for preparing the edible coated compositions.
2. Description of the Prior Art
Tablet coating is well known in the art. In general, the coating of a tablet involves the application of a primary coat (sealing coat), a subcoat, a sugar or sugarless syrup coat (grossing, heavy syrup coat, regular syrup coat), a finishing coat and a polishing coat (waxing coat). Tablets are coated to mask unpleasant taste, odor, and texture, to protect sensitive core ingredients from decomposition, and to improve the appearance and esthetic appeal of the tablet.
A frequent problem in tablet coating is that water from the coating layer solutions can migrate into the core material during the coating process or during subsequent storage. This water can cause swelling and subsequent cracking, bursting and clumping of the coated tablets. The purpose of the primary coat, which is applied directly over the uncoated tablet, is to seal and protect the core material from the water used in subsequent coating steps. Moisture absorption by the core is a particularly difficult problem when the core material is a very hygroscopic material such as a sugar alcohol. In addition, components in the core material, such as acidulants, can react with components in the coating layer solution, such as carbonates, and give the color of the final tablet a mottled appearance.
U.S. Pat. No. 4,673,577, issued to Patel and assigned to Wm. Wrigley Jr. Company, discloses a chewing gum which contains a shellac encapsulated intense sweetening agent.
U.S. Pat. No. 4,238,510, issued to Cherukuri et al. and assigned to Life Savers, Inc., discloses a sorbitol coated edible composition wherein sorbitol is present in the coating layer in an amount from about 45% to about 90% by weight. The coating may also contain mannitol and hydrogenated starch hydrolysates.
U.S. Pat. No. 4,643,894, issued to Porter et al. and assigned to Colorcon, Inc., discloses a maltodextrin coated pharmaceutical such as an aspirin.
U.S. Pat. No. 4,511,553, issued to Boesig et al. and assigned to Meggle Milchindustrie GmbH & Co. KG, discloses a coating process wherein the coating layer solution consists essentially of saccharose, at least one additional sugar, and water.
U.S. Pat. No. 4,610,891, issued to Miyamoto et al. and assigned to Zeria Shinyaku Kogu Kabushiki Kaisha, discloses a method for coating a pharmaceutical wherein the coating layer solution comprises an aqueous solution of sucrose and pullulan.
U.S. Pat. No. 3,832,473, issued to Sahaydak and assigned to Warner-Lambert Company, discloses a method for preparing pressed mints wherein the mints contain from about 1% to about 10% of a solid encapsulated flavoring agent which comprises a flavor oil emulsified in a mixture of corn syrup solids, an emulsifying agent, and glycerol or a nontoxic glycol.
Principles of Pharmaceutical Processing, Chapter 10, pp. 202-203, discloses that cellulose acetate phthalate, zein, shellac and certain resins may be used as the primary coating layer to protect core materials from water in sugar coating processes.
U.S. Pat. No. 4,753,790, issued to Silva et al. and assigned to Warner-Lambert Company, discloses a method for preparing a sorbitol coated edible composition which comprises applying to a substantially anhydrous edible core material a first coating solution which comprises (a) about 77% to about 81% by weight sorbitol solution comprising about 65% to about 75% by weight sorbitol, (b) about 9.5% to about 12.5% by weight crystalline sorbitol powder, (c) about 0.25% to about 1.5% by weight of at least one film-forming agent, and (d) about 0.1% to about 5.0% by weight of at least one crystallization retarding agent, and a second coating solution which comprises (a) about 82% to about 92% by weight sorbitol solution comprising about 65% to about 75% by weight sorbitol, (b) about 1.0% to about 2.5% by weight crystalline sorbitol powder, (c) about 0.05% to about 2.0% by weight of at least one film-forming agent, and (d) about 0.1% to about 0.3 % by weight of at least one crystallization retarding agent.
Accordingly, many different types of coating materials are known to protect different types of core materials. None of the above references, however, discloses a primary coating material suitable for protecting very hygroscopic core materials such as sugar alcohols. Hence, there is a need for a primary coating layer to protect sugar alcohol core materials from moisture. Such moisture protected sugar alcohol cores would be useful as ingestible compositions by providing non-cariogenic edible compositions. The present invention provides such moisture protected sugarless core compositions and the ingestible compositions in which the moisture protected sugarless core compositions may be incorporated.